Anthropomorphic transradial myoelectric hand using tendon-spring mechanism

In the developing countries, the need for prosthetic hands is increasing. In general, transradial amputee patients use prosthetic hands that are passive like a body-powered prosthesis. This research proposes a low-cost myoelectric prosthetic hand based on 3D printing technology. Hand and finger size were designed based on the average size of human hands in Indonesia. The proposed myoelectric hand employs linear actuator combined with the tendon-spring mechanism. Myoelectric hand was developed with five modes of grip pattern to perform various object grasping in activity of daily living. Control strategy had been developed for controlling the motion of flexion and extension on the hand and saving the energy consumed by the actuators. The control strategy was developed under MATLAB/Simulink environment and embedded to Arduino Nano V3 using Simulink Support Package for Arduino Hardware. Surface electromyography (EMG) sensor was used in this research for reading the muscle activity of the user/wearer. The proposed myoelectric hand had been tested in object grasping test and was implemented on a study participant with transradial amputee

메타표면을 가지는 S밴드 형상기억합금 마이크로 구동기의 레이저를 이용한 선택적 구동

학위논문(석사)--서울대학교 대학원 :공과대학 기계항공공학부,2019. 8. 안성훈.Shape Memory Alloys (SMAs) have been widely researched as actuators because SMAs have advantages in high force density and deformable structures. The SMA actuator has a lower actuation speed. To overcome this limit, there have been researched to reduce the size of the actuator to the micro scale in order to use the scale effect of heat transfer. The SMA micro actuator showed higher actuation speed and heat transfer rate than the meso scale actuator. In this research, S-bend shaped actuators were studied to make a SMA micro actuator. In addition, a metasurface was designed and fabricated on the actuator to enhance the absorption of the laser light at 785 nm wavelength. The metasurface was a lattice array of subwavelength nano cavities, and designed to minimize the reflectance of light at a wavelength of 785 nm. Focused Ion Beam (FIB) was used to fabricate the SMA micro actuator and the metasurface. It was experimentally confirmed that the actuation length of the SMA micro actuator with the metasurface was about twice longer than that without metasurface. It is expected that the absorption spectra of SMA micro actuators can be changed by using the metasurface.형상기억합금(Shape Memory Alloy, SMA)는 높은 힘 밀도와 변형 가능한 구조를 가지는 장점 덕분에 구동기로서 연구되어왔다. 형상기억합금 구동기는 구동력에 비해 낮은 구동속도를 가지고 있어, 이를 극복하기 위해 크기 효과 (Size effect)를 이용하고자 구동기의 크기를 마이크로 수준으로 낮추는 연구가 진행되어왔다. 이렇게 연구된 형상기억합금 마이크로 구동기는 메소스케일 구동기와 비교하면 보다 높은 구동 속도, 변형률, 열 전달률을 가진다. 전기저항으로 온도를 제어하는 대신 마이크로 스케일에서는 자외선 파장의 레이저로 구동되는 특징을 보인다. S밴드 형상을 가지는 마이크로 구동기를 제안하였고, 구동원을 가시광선 및 적외선 영역으로 확장하고자 메타표면(Metasurface)을 구동기 표면에 제작하였다. 메타표면은 파장 이하 길이를 가지는 나노 홈 격자 구조로 이루어져 있으며, 785 nm 파장의 빛의 반사율을 최소화하는 방향으로 설계되었다. 형상기억합금 마이크로 구동기 및 메타표면을 제작하기 위해 집속이온빔(Focused Ion Beam, FIB)이 사용되었다. 결과적으로, 785 nm 파장의 구동원에서 메타표면을 가지는 형상기억합금 마이크로 구동기의 구동 길이가 메타표면을 가지지 않는 구동기보다 약 223% 더 긴 것을 실험적으로 확인하였다. 본 연구를 통해 형상기억합금 마이크로 구동기의 구동원을 확장할 수 있고, 구동원에 따라 선택적으로 구동을 할 수 있을 것으로 기대한다.Chapter 1. Introduction 1 1.1. Study background 1 1.1.1. Shape memory alloy (SMA) and SMA micro actuator 1 1.1.2. Metasurface and light absorber 3 1.1.3. Focused ion beam fabrication 6 1.2. Purpose of research 8 Chapter 2. S-bend SMA micro actuator 9 2.1. Design and Fabrication 9 2.2. Computational Analysis 12 2.3. Evaluation of SMA micro actuators 15 Chapter 3. Metasurface on SMA micro actuator 21 3.1. Machinability of the metasurface 21 3.2. Design of metasurface 23 3.3. Evaluation of the metasurface 28 3.3.1. Fabrication and preparations 28 3.3.2. Results 33 Chapter 4. Conclusion 35 Bibliography 37 Abstract in Korean 41Maste

Finite element modeling and simulation of a robotic finger actuated by Ni-Ti shape memory alloy wires

In this paper, a dynamic model for an artificial finger driven by Shape Memory Alloy (SMA) wires is presented. Due to their high energy density, these alloys permit the realization of highly compact actuation solutions with potential applications in many areas of robotics, ranging from industrial to biomedical ones. Despite many advantages, SMAs exhibit a highly nonlinear and hysteretic behavior which complicates system design, modeling, and control. In case SMA wires are used to activate complex robotic systems, the further kinematic nonlinearities and contact problems make the modeling significantly more challenging. In this paper, we present a finite element model for a finger prototype actuated by a bundle of SMA wires. The commercially available software COMSOL is used to couple the finger structure with the SMA material, described via the Muller-Achenbach-Seelecke model. By means of several experiments, it is demonstrated how the model reproduces the finger response for different control inputs and actuator geometries

Biomimetic Prosthetic Hand Enabled by Liquid Crystal Elastomer Tendons.

As one of the most important prosthetic implants for amputees, current commercially available prosthetic hands are still too bulky, heavy, expensive, complex and inefficient. Here, we present a study that utilizes the artificial tendon to drive the motion of fingers in a biomimetic prosthetic hand. The artificial tendon is realized by combining liquid crystal elastomer (LCE) and liquid metal (LM) heating element. A joule heating-induced temperature increase in the LCE tendon leads to linear contraction, which drives the fingers of the biomimetic prosthetic hand to bend in a way similar to the human hand. The responses of the LCE tendon to joule heating, including temperature increase, contraction strain and contraction stress, are characterized. The strategies of achieving a constant contraction stress in an LCE tendon and accelerating the cooling for faster actuation are also explored. This biomimetic prosthetic hand is demonstrated to be able to perform complex tasks including making different hand gestures, holding objects of different sizes and shapes, and carrying weights. The results can find applications in not only prosthetics, but also robots and soft machines. &nbsp;</p

Development of a 4D hand gripping aid using a knitted shape memory alloy and evaluation of finger-bending angles in elderly women

As the global population ages, there is an increasing demand for physical assistive devices for the elderly. This study aimed to develop and evaluate a wearable gripping aid for elderly women to assist in their handgrip ability. We developed an actuator module for the hand-gripping aid using a 4D knitted shape memory alloy and attached to a flexible nylon glove. At baseline, we measured the bending angles of the knitted shape memory alloy and the subjects fingers while gripping. The bending angles of the gripping aid demonstrated similar hand mobility to those of elderly women in real life. We also found that SMA modules attached to a glove could implement the bending angle when gripping a ball derived from the index and middle fingers of elderly women. The finding could help to develop hand products that could be worn on the hand of the elderly by realizing the bending motion of each finger. The outcomes of this study suggest the practical potential of this wearable device as an effective hand-gripping aid for the elderly, based on a novel 4D material and ergonomic design approach.This work was supported by Seoul National University Research Grant in 2021 and the National Research Foundation of Korea (NRF) grant funded by the Korean Government (MSIT) (2016R1A5A1938472)

Extraction of the underlying material response of pseudoelastic NiTi and its application in numerical simulations

In certain temperature regimes NiTi exhibits pseudoelasticity, meaning that after being loaded to strains of 6-7% it can return to its original configuration. This behavior is produced by the reversible solid-state phase transformation between the austenitic (A) and martensitic (M) phases. During isothermal tensile testing the response produces a closed hysteresis that traces two stress plateaus corresponding to localization and propagation of transformation front(s). Hallai and Kyriakides (2013) extracted the underlying up-down-up material response during the A [rightwards arrow symbol] M transformation from an experiment on a laminate composed of an unstable NiTi core and hardening facestrips. In these experiments, the laminates were plastically deformed to a strain of about 6%. To obtain the underlying response during the reverse M [rightwards arrow symbol] A transformation, the laminate must be reverse loaded back to zero, resulting in compressive forces in the hardening facestrips which ultimately lead to the laminate buckling. This thesis presents a new experimental setup to prevent buckling by laterally supporting the laminate during reverse loading. From this test, the complete underlying NiTi response is extracted and exhibits the expected softening branches during both the A [rightwards arrow symbol] M and M [rightwards arrow symbol] A transformations, with each branch having a Maxwell stress similar to the corresponding experimental plateau stress level. The full response is used to calibrate a custom constitutive model that produces a fit based completely on a measured response for the first time. Simulations of the isothermal tensile tests using this fit capture the measured response and localized deformation pattern to the greatest extent thus far. The fit is also used to conduct a parametric study on the effect the hardening facestrip thickness has on the overall laminate response, and possible changes to aid future users of this method are identified. The new method presented can replace the previously empirical model calibration method and enable more confident modeling of the unstable behavior of SMA structures through the use of measured data.Aerospace Engineerin

Additive manufacturing of sustainable biomaterials for biomedical applications

Biopolymers are promising environmentally benign materials applicable in multifarious applications. They are especially favorable in implantable biomedical devices thanks to their excellent unique properties, including bioactivity, renewability, bioresorbability, biocompatibility, biodegradability, and hydrophilicity. Additive manufacturing (AM) is a flexible and intricate manufacturing technology, which is widely used to fabricate biopolymer-based customized products and structures for advanced healthcare systems. Three-dimensional (3D) printing of these sustainable materials is applied in functional clinical settings including wound dressing, drug delivery systems, medical implants, and tissue engineering. The present review highlights recent advancements in different types of biopolymers, such as proteins and polysaccharides, which are employed to develop different biomedical products by using extrusion, vat polymerization, laser, and inkjet 3D printing techniques in addition to normal bioprinting and four-dimensional (4D) bioprinting techniques. This review also incorporates the influence of nanoparticles on the biological and mechanical performances of 3D-printed tissue scaffolds. This work also addresses current challenges as well as future developments of environmentally friendly polymeric materials manufactured through the AM techniques. Ideally, there is a need for more focused research on the adequate blending of these biodegradable biopolymers for achieving useful results in targeted biomedical areas. We envision that biopolymer-based 3D-printed composites have the potential to revolutionize the biomedical sector in the near future

Bio-Mimetic Smart System Functioning Like Natural Skin and Muscle

Soft machines, or soft robotics, are emerging technologies bringing many exciting prospects for the coming future. Creating soft machines with biomimetic functions is of key importance for applications in bettering human life and creating more complex robotic systems. Various mechanisms have been adopted to mimic natural tactile sense, tough, muscular motion, and even artificial intelligence. Among these, developing a bio-mimetic system capable of self-healing and degradation that behaves like a muscular hydrostat is appealing for soft robotics. This thesis will mainly focus on developing both artificial skin and artificial muscles that can self-heal, be recycled, and function like biological tissue. To develop a biomimetic artificial skin, we adopted an imine-bonded polymer as the main component, and embedded silver nanoparticles as well as liquid metals to create conductive components. Our artificial skin is capable of re-healing and recycling, and can be mounted to a complex 3D surface without introducing damage and strains. Such artificial skin, at the same time, can sense pressure and temperature change, flow across the surface, and humidity change in the atmosphere. Recyclability enables this platform to not only serve as an artificial skin, but also for other electronics applications. The artificial muscles were also developed for this project based on a recently invented Liquid Crystal Elastomer, whose behavior is most similar to that of natural muscles. To achieve large actuation strains, a fast response, and small scale local controlling, a Liquid Metal was introduced for stimulating the artificial muscle. Over 100% linear contracting strain was realized based on such a combination, which is greater than that of natural muscles. Bending and twisting deformation were also realized easily on such system. To further demonstrate the advantages of our artificial muscle, we integrated it into other passive soft elastomers like Ecoflex to mimic the camouflage behavior of cephalopods

Design and Fabrication of Soft 3D Printed Actuators: Expanding Soft Robotics Applications

Soft pneumatic actuators are ideal for soft robotic applications due to their innate compliance and high power-weight ratios. Presently, the majority of soft pneumatic actuators are used to create bending motions, with very few able to produce significant linear movements. Fewer can actively produce strains in multiple directions. The further development of these actuators is limited by their fabrication methods, specifically the lack of suitable stretchable materials for 3D printing. In this thesis, a new highly elastic resin for digital light projection 3D printers, designated ElastAMBER, is developed and evaluated, which shows improvements over previously synthesised elastic resins. It is prepared from a di-functional polyether urethane acrylate oligomer and a blend of two different diluent monomers. ElastAMBER exhibits a viscosity of 1000 mPa.s at 40 °C, allowing easy printing at near room temperatures. The 3D-printed components present an elastomeric behaviour with a maximum extension ratio of 4.02 ± 0.06, an ultimate tensile strength of (1.23 ± 0.09) MPa, low hysteresis, and negligible viscoelastic relaxation